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Full text of "Modern Mechanical Engineering Vol-I"

Fitting and Erecting of Heavy

The assembly and erection of heavy machinery of all types calls for
not only the skill and care which the handling of large plant requires, but,
to a very large degree, for the judgment which is partly intuitive and partly
the result of wide and all-round experience. So many problems arise in
the erection of plant on site, as compared with its erection at the makers'
works, where all the usual facilities exist, that success or failure depends
very largely on the ability to size up a difficulty correctly, and then devise
ways and means of producing the best possible results. It is not possible,
therefore, in an article of this kind, to give complete directions for the assembly
and erection of all kinds of heavy plant, as the conditions to be met with
vary so greatly; the aim of the article will be to deal with the kind of problems
that arise and the various means taken to meet them. It will probably be
conceded that, if the problems which arise in the erection of a large steam-
turbine electric generating set and condensing plant be considered, the
ground will cover most of the problems that arise when handling less com-
plicated plants. The article will deal, therefore, with a plant of this de-
scription, and some general notes will be added on the application of the
principles to the erection of special plants.

Foundations.—These are almost invariably made of concrete nowa-
days, though in certain cases brick is used for cheapness and where the
weights to be supported are not very heavy and are not subjected to shock.
In general, it is advisable to make the lowest part of the foundation block
in the form of a concrete float or raft on which the main foundation block
is built. The dimensions of this concrete raft depend on the nature of
the subsoil; where this is soft or friable, the area of the raft must be corre-
spondingly large in order to lessen the weight, per square foot on the raft,
of the superimposed machinery. Where the subsoil is particularly soft, it
will probably be necessary to drive a large number of piles first, round the
heads of which the concrete raft is built. It should be the first duty of the
engineer in charge of erection of machinery to satisfy himself regarding the
suitability of the foundations and the subsoil. In general, the foundations
are provided by the customer to the drawings of the contractors who supply